1. Technical Field
The present invention relates to semiconductor a device having a protective element.
2. Related Art
For the case where a protective element for protecting an internal circuit from static electricity or the like is provided to a semiconductor device, it is most general to arrange a resistive element for limiting current between the protective element and the internal circuit, to thereby prevent over-current from flowing into the internal circuit. The resistive element is typically a polysilicon resistor composed of polysilicon, or a diffusion layer resistor composed of a diffusion layer. In some cases where the diffusion layer resistor is used, it may be integrated with the protective element so as to reduce the occupied area (see Japanese Laid-Open Patent Publication Nos. 02-070229 and 06-302765, for example).
Alternatively, as shown in Japanese Laid-Open Patent Publication Nos. 10-150109 and 2005-109163, there are proposed a bipolar transistor protective element and a diode protective element, both having a large number of dot-patterned diffusion layers arranged to form an array. These dot-patterned protective elements may be increased in the length of opposition between the emitter and collector, or between the cathode and anode, and may consequently have larger protection tolerance, as compared with those of the bipolar transistor protective element and diode protective element, which make use of a diffusion layer having a large area.
However, the diffusion layers of the dot-patterned protective elements are extremely small, so that it may be difficult to use the diffusion layers as the diffusion layer resistor. For this reason, the semiconductor device has been configured to have an additional resistor typically using polysilicon, provided to the external of the dot-patterned protective element, only to enlarge the semiconductor device.